iCloud Custom Email Domain - Can 2 people use the same email address that have different Apple ID’s.

When using a custom domain with ICloud Mail, I see I can share the domain with other family members, but can we use/share the same email address?

My wife and I use the same email (IMAP/POP on another provider) and want to continue to use the same email on our own devices with different Apple ID’s?

It looks like that is a limitation and can’t be done, but want to confirm before I find a different provider.

Thanks you!